Adds CustomField#group_statement.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@10071 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/custom_field.rb

@@ -128,7 +128,7 @@ class CustomField < ActiveRecord::Base
 
   # Returns a ORDER BY clause that can used to sort customized
   # objects by their value of the custom field.
-  # Returns false, if the custom field can not be used for sorting.
+  # Returns nil if the custom field can not be used for sorting.
   def order_statement
     return nil if multiple?
     case field_format
@@ -151,6 +151,18 @@ class CustomField < ActiveRecord::Base
     end
   end
 
+  # Returns a GROUP BY clause that can used to group by custom value
+  # Returns nil if the custom field can not be used for grouping.
+  def group_statement 
+    return nil if multiple?
+    case field_format
+      when 'list', 'date', 'bool', 'int'
+        order_statement
+      else
+        nil
+    end
+  end
+
   def <=>(field)
     position <=> field.position
   end